Light emitting diodes (LEDs) are semiconductor light-emitting devices that convert current into light. As luminance of LEDs has been recently increased, the LEDs are being used as light sources for displays, vehicles, and illumination. Also, LEDs emitting highly efficient white light may be realized by using a fluorescent substance or combining LEDs having various colors.
Since such a LED has general diode characteristics, when the LED is connected to an alternative current (AC) power source, the LED is repeatedly turned on/off according to a direction of the current. Thus, the LED does not continuously generate light. In addition, the LED may be damaged by the reverse current.
Thus, various researches are conducted in cases which an LED is directly connected to an AC power source to facilitate use of the LED.